Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that allows developers to send notifications and messages to Android, iOS, and web applications. Here’s how it works:
1. Message Flow
- App Registers with FCM: The client app (Android/iOS/Web) registers with FCM and receives a registration token.
- Server Sends a Message: The backend server sends a message to FCM, specifying the target device or topic.
- FCM Delivers the Message: FCM routes the message to the correct device, ensuring reliable delivery.
2. Types of Messages
- Notification Messages: Display messages automatically in the system notification tray.
- Data Messages: Deliver custom data payloads to the app for background processing.
3. Key Features
- Topic Messaging: Send messages to multiple users subscribed to a specific topic.
- Device Targeting: Send messages to specific devices using their registration tokens.
- Condition Messaging: Use logical expressions to target multiple user segments.
- Scheduled & Prioritized Delivery: FCM allows setting priorities and conditions for message delivery.
4. Architecture
- Client App: Receives and handles messages.
- FCM Backend: Routes and manages message delivery.
- Application Server: Triggers and sends messages using FCM APIs.
5. Delivery Mechanism
- On Android, FCM uses Google Play Services for efficient delivery.
- On iOS, it integrates with APNs (Apple Push Notification Service).
- On Web, it uses Web Push protocols.
